A cardiac arrhythmia is a condition in which the heart's normal rhythm is disrupted. There are many types of cardiac arrhythmias, including supraventricular arrhythmias that begin above the ventricles (such as premature atrial contractions, atrial flutter, accessory pathway tachycardias, atrial fibrillation, and AV nodal reentrant tachycardia), ventricular arrhythmias that begin in the lower chambers of the heart (such as premature ventricular contractions, ventricular tachycardia, ventricular fibrillation, and long QT syndrome), and bradyarrhythmias that involve slow heart rhythms and may arise from disease in the heart's conduction system.
Certain types of cardiac arrhythmias, including ventricular tachycardia and atrial fibrillation, may be treated by ablation (for example, radiofrequency (RF) ablation, cryoablation, ultrasound ablation, laser ablation, microwave ablation, and the like), either endocardially or epicardially. For example, atrial fibrillation (AF) is frequently treated with pulmonary vein ablation (also called pulmonary vein antrum isolation, or PVAI), a procedure that may involve inserting a guide wire and then a mapping device into a pulmonary vein (PV) to map electrical impulses within the vein. Once the mapping catheter is properly seated within the PV, an ablation element (such as a cryoballoon or RF ablation device) is advanced over the mapping catheter until it is in contact with the ostium of the PV, within the left atrium. After ablation of the ostial tissue, the mapping catheter may then be used to confirm PV isolation. That is, the mapping catheter may be used to determine whether aberrant electrical conductivity is still present.
When a cryoballoon is used as the ablation element in a PVAI procedure, it is desirable that the cryoballoon is in complete contact with the PV ostial tissue so as to totally occlude the PV. Therefore, such a PVAI procedure may include a step between positioning the device at the PV ostium and activating the ablation element wherein contrast dye is injected from the device into the pulmonary vein to assess vein occlusion. Fluoroscopy may be used to visualize the contrast dye to determine whether any of the dye escapes from the pulmonary vein into the left atrium. For example, if the cryoballoon forms a tight seal against the ostium, no dye will be able to escape into the left atrium. If the cryoballoon is not properly seated, on the other hand, fluoroscopy may show the presence of contrast dye in the left atrium.
Although the use of contrast is effective and generally safe, it is desirable to introduce as few components, including chemicals, into a patient as possible. Further, the use of contrast dye necessitates the extra step of fluoroscopic visualization, which can be time consuming and requires additional equipment.
It is desirable, therefore, to provide a system that combines mapping and occlusion verification capabilities with an ablation device to provide real-time physiological data and to simplify a PVAI procedure.